[Insight-developers] Copying the state of the TimeVaryingVelocityFieldTransform

[Williams, Norman K]

So what you're saying is that at the point where you want to copy a
transform of that type, what you really care about is the data actually
contained in the deformation field?  This feels like shaky ground to me,
for a number of reasons, When is a transform's internal state not relevant
to a copy of that transform? Should state variables that are only used
when computing the transforms be explicitly labeled as such.

--
Kent Williams norman-k-williams at uiowa.edu






On 11/15/11 9:24 AM, "Nicholas Tustison" <ntustison at gmail.com> wrote:

>Hi Kent,
>
>Thanks for tackling this.  I would opt for not saving the velocity field.
>I suspect that when somebody gets to the stage of writing out the
>transforms for storage, they're more concerned with the transformation
>itself and not so much with how they arrived at the transformation
>and the velocity field would fall under the latter category.
>
>Nick
>
>
>On Nov 15, 2011, at 10:16 AM, Williams, Norman K wrote:
>
>> I've been working on a patch to allow Transforms to be copied.  This
>> addresses a gap in the API for transforms: If you read a transform file,
>> you only have read-only access to the transforms.  You can manually copy
>> parameters from the const Transform to a newly instantiated transform of
>> the same type, but this raises two problems:
>>
>> 1. Transform state does not exist solely in the Parameters &
>> FixedParameters, for several types of Transform.  If you need to make a
>> copy you need to know how the internal state has been augmented with
>>'out
>> of band' parameters.
>>
>> 2. To copy a CompositeTransform, it would need to copy all its
>>constituent
>> transforms.
>>
>> Adding a Clone method gives us a way to copy transforms in a single
>> method, and the transforms themselves are responsible for overriding
>>Clone
>> to make sure the entire state is transformed.
>>
>> The TimeVaryingVelocityFieldTransform is the one case where I am not
>>sure
>> about how to copy the internal state. It is a subclass of
>> DisplacementField, but it has an additional Image-like member, the
>> TimeVaryingVelocityField. Plus it also has an interpolator member. Do
>> these all need to be copied?
>> --
>> Kent Williams norman-k-williams at uiowa.edu
>>
>>
>>
>>
>>
>>
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